WeiSen 4-Pin Trailer Wiring Harness Installation Manual

1. Introduction

This manual provides detailed instructions for the proper installation and operation of your WeiSen 4-Pin Trailer Wiring Harness. This harness is designed to provide a standard 4-pin flat connector for connecting trailer tail lights, brake lights, and turn signals, ensuring safe towing. Please read all instructions carefully before beginning installation.

2. Product Overview

The WeiSen 4-Pin Trailer Wiring Harness features SMT circuitry for reliable electrical conductivity and a plug-and-play design for simplified installation. It includes all necessary components for connecting to your vehicle's existing wiring system.

Figure 2.1: Diagram illustrating the main components of the wiring harness and their connections.

2.1 Key Features

• 4-Pin Trailer Wiring Connector: Provides standard connections for trailer tail lights, brake lights, and turn signals.
• Vehicle-Side Harness: Designed for direct connection to your vehicle's tail light assembly.
• SMT Circuitry: Ensures stable power output and electrical safety.
• Plug & Play Design: Facilitates easy installation without cutting or splicing wires.
• Protective Rubber Boots: Shields connections from dust, moisture, and corrosion.

Figure 2.2: The standard 4-pin trailer wiring connector with its protective cap, highlighting the plug-and-play design.

3. Compatibility

This WeiSen 4-Pin Trailer Wiring Harness (Model 70DA206005) is compatible with the following Toyota vehicles:

• Toyota RAV4: 2013-2018
• Toyota Avalon: 2013-2018
• Toyota Camry: 2018

Figure 3.1: Visual representation of compatible Toyota RAV4 and Avalon models.

4. Package Contents

Verify that all items listed below are present in your package:

• 1 x 4-Pin Trailer Wiring Harness (with integrated black signal converter)
• Plug & Play Vehicle-Side Connectors
• Red Fuse and Fuse Holder
• Power Connection Wire
• Assorted Wiring Components (e.g., zip ties, ring terminal, splice connectors)

Figure 4.1: All components included in the wiring harness kit.

5. Safety Information

Always prioritize safety during installation. Failure to follow these guidelines may result in injury or damage to your vehicle.

• Disconnect the vehicle's negative battery terminal before starting any electrical work.
• Wear appropriate personal protective equipment, including safety glasses.
• Ensure the vehicle is parked on a level surface with the parking brake engaged.
• Do not exceed the specified amperage ratings for the tail light (6.0 Amps) and turn/brake circuits (3.0 Amps).
• Route all wiring away from hot surfaces, sharp edges, and moving parts. Secure wiring with zip ties.
• If you are unsure about any step, consult a qualified automotive technician.

6. Installation Instructions

Follow these steps carefully to install your WeiSen 4-Pin Trailer Wiring Harness.

6.1 Preparation

1. Ensure the vehicle is off and the parking brake is engaged.
2. Disconnect the negative battery terminal.
3. Open the vehicle's rear hatch or trunk to access the cargo area.
4. Locate and carefully remove the necessary interior trim panels to access the vehicle's tail light wiring harnesses. This typically involves removing fasteners and gently prying panels. Refer to your vehicle's service manual if needed.

6.2 Harness Connection

5. Identify the vehicle's tail light wiring harnesses. There will be one on the driver's side and one on the passenger's side.
6. On the driver's side, disconnect the factory wiring harness from the tail light assembly.
7. Take the WeiSen harness with the black converter box. Connect the appropriate vehicle-side plug-and-play connector (typically the one with more wires) inline with the disconnected factory harness. One end plugs into the vehicle's wiring, and the other plugs into the tail light assembly.


Figure 6.1: Example of a vehicle-side plug-and-play connector.

8. Locate a suitable flat, clean surface within the vehicle's rear cargo area, preferably near the driver's side tail light, to mount the black converter box. Use the provided double-sided adhesive pad to secure the box.
9. Route the green wire from the converter box across the vehicle's rear to the passenger's side tail light assembly. Secure it neatly under trim panels or carpeting.
10. On the passenger's side, disconnect the factory wiring harness from the tail light assembly. Connect the green wire's plug-and-play connector inline with the disconnected factory harness, similar to step 7.


Figure 6.2: Another example of a vehicle-side plug-and-play connector.

6.3 Power Connection

11. Locate the red power wire with the inline fuse holder. Connect one end of this wire to the black converter box (usually a single red wire connection point).
12. Route the power wire from the converter box to the vehicle's battery. This typically involves routing it through a grommet in the vehicle's floor or firewall to the underside of the vehicle, then along the frame or existing wiring harnesses, and finally into the engine compartment to the positive battery terminal. Use zip ties to secure the wire every 12-18 inches, keeping it away from hot or moving parts.
13. Once the power wire reaches the engine compartment, attach the provided ring terminal to the end of the power wire.
14. Connect the ring terminal to the positive (+) terminal of the vehicle's battery.


Figure 6.3: The inline fuse holder, which protects the power circuit.

6.4 Final Steps

15. Reconnect the vehicle's negative battery terminal.
16. Test the trailer wiring harness by connecting a trailer or a trailer light tester. Verify that all tail lights, brake lights, and turn signals function correctly.
17. Once confirmed, reinstall all removed interior trim panels.
18. Store the 4-pin trailer connector inside the vehicle's cargo area when not in use, or route it to a convenient exterior location if preferred, ensuring it is secured and protected from the elements.

Figure 6.4: The standard 4-pin trailer wiring connector.

7. Operating Instructions

To use your WeiSen 4-Pin Trailer Wiring Harness:

1. Ensure the vehicle is off before connecting or disconnecting a trailer.
2. Remove the protective cap from the 4-pin trailer connector.
3. Align the 4-pin connector with the corresponding receptacle on your trailer. Push firmly to ensure a secure connection.
4. Once connected, verify that the trailer's lights (tail lights, brake lights, turn signals) are functioning correctly by testing them from the vehicle.
5. When towing is complete, disconnect the trailer harness and replace the protective cap on the vehicle's 4-pin connector to prevent corrosion and damage.

8. Troubleshooting

If you encounter issues with your trailer wiring harness, refer to the following common problems and solutions:

9. Specifications

• Item: 4-Pin Trailer Wiring Harness
• Model Number: 70DA206005
• Material: SMT Circuitry
• Design: Plug & Play
• Tail Light Circuits: 6.0 Amps
• Turn and Brake Circuits: 3.0 Amps
• Connector Type: 4-pin Trailer
• Item Weight: 0.74 Kilograms (approx. 1.63 Pounds)

10. Maintenance

To ensure the longevity and reliable performance of your wiring harness:

• Keep the 4-pin connector clean and free of dirt, debris, and moisture. Use the protective cap when not in use.
• Periodically inspect all wiring for signs of wear, fraying, or damage. Replace any damaged components immediately.
• Check electrical connections for corrosion. Apply dielectric grease to terminals to prevent corrosion, especially in humid or corrosive environments.

11. Warranty and Support

For warranty information or technical support, please refer to the documentation provided with your purchase or contact WeiSen customer service through their official channels. Keep your proof of purchase for warranty claims.